The disclosure of Japanese Patent Application No. 2000-364299 filed on Nov. 30, 2000, including the specification, drawings and abstract, is incorporated herein by reference in its entirety.
1. Field of Invention
The invention relates to a regeneration control apparatus and method for a vehicle, and more particularly to a shift control of a transmission performed at the time of power generation through regeneration control of a rotation device.
2. Description of Related Art
A known vehicle has: (a) an internal combustion engine connected to a drive wheel of the vehicle via a transmission capable of changing the speed ratio; (b) a connection-disconnection device that is engaged to allow and is disengaged to prohibit power transfer between the internal combustion engine and the transmission; (c) a rotation device that is connected to the drive wheel via the transmission and that functions at least as an electric power generator; and (d) a regeneration controller that, during the running of the vehicle, causes the rotation device to generate electric power through regeneration control of the rotation device and applies a braking force to the vehicle.
An example of such vehicles is a hybrid vehicle described in Japanese Patent Application Laid-Open No. 8-251708, in which the rotation device is a motor-generator that selectively functions as both a power generator and an electric motor, and the transmission is a belt-type continuously variable transmission. During the regeneration control by the regeneration controller, the speed shift of the transmission is controlled so that the motor-generator rotates at a rotation speed that provides the highest power generating efficiency.
However, if the speed shift control is performed based only on the electric power generating efficiency of the motor-generator, a problem in energy efficiency occurs as follows. That is, if the connection device is engaged and therefore the internal combustion engine is passively turned by the rotation of the motor-generator, braking force is generated by the turning resistance of the engine due to the pump effect, friction loss, etc., so that the amount of electric power generated by the motor-generator (regenerative braking torque) decreases. Thus, energy efficiency deteriorates. During the regeneration control, it is appropriate to disengage the connection-disconnection device and thereby disconnect the engine. However, there are cases where the regeneration control must be performed while the connection-disconnection device is engaged so that the engine is passively turned, including a case where quick supply of drive power from the internal combustion engine is needed, for example, during a re-acceleration in a high-speed vehicle run during which a sufficient drive power cannot be produced by the electric motor alone.
Accordingly, it is one object of the invention to make it possible to achieve excellent power generating efficiency even when regeneration control is performed while the passive turning of the engine is allowed.
In order to achieve the aforementioned and/or other objects, one aspect of the invention provides a regeneration control apparatus for a vehicle that includes (a) an internal combustion engine connected to a drive wheel of the vehicle via a transmission capable of shifting a speed ratio, (b) a connection-disconnection device that is selectively engaged to allow and disengaged to prohibit a power transfer between the internal combustion engine and the transmission, and (c) a rotation device that is connected to the drive wheel via the transmission and that functions at least as an electric power generator. The regeneration control apparatus further has a controller that (d) performs a regeneration control of the rotation device so that the rotation device generates electricity and applies a braking force to the vehicle during running of the vehicle, and that (e) during the regeneration control, selectively controls the speed ratio of the transmission on different bases depending on whether the connection-disconnection device is in a connected state or a disconnected state.
The invention also provides a method of controlling regeneration of electric power in a vehicle that includes (a) an internal combustion engine connected to a drive wheel of the vehicle via a transmission capable of shifting a speed ratio, (b) a connection-disconnection device that is selectively engaged to allow and disengaged to prohibit a power transfer between the internal combustion engine and the transmission, and (c) a rotation device that is connected to the drive wheel via the transmission and that functions at least as an electric power generator. In the control method, the speed ratio of the transmission is controlled on different bases depending on whether the connection-disconnection device is determined to be in a connected state or a disconnected state, when a request for deceleration of the vehicle is made. The regeneration control of the rotation device is performed so as to generate electricity and apply a braking force to the vehicle.
In the regeneration control apparatus and method for a vehicle according to this aspect of the invention, the shift control of the transmission is performed on different bases depending on whether the connection-disconnection device is in the engaged state, such that the engine is passively turned, or the disengaged state, such that the engine is disconnected. Therefore, during each of the states, the regeneration control of the rotation device can be performed at excellent energy efficiency.